Device for supplying temperature dependent negative voltage

1. A negative voltage supply device, comprising: a first negative voltage detector for detecting a level of a negative voltage to output a first detection signal indicating that the level of the negative voltage is less than a first voltage; a second negative voltage detector for detecting a level of the negative voltage to provide a second detection signal indicating that the level of the negative voltage is less than a second voltage which is lower than the first voltage; a third negative voltage detector for detecting a level of the negative voltage to generate a third detection signal indicating that the level of the negative voltage is less than a third voltage varying with temperature; a clamping part for logically combining the first detection signal, the second detection signal, and the third detection signal to output a fourth detection signal causing a level of the negative voltage to be dependent on temperature between the first voltage and the second voltage; and a negative voltage pumping unit for pumping the negative voltage in response to the fourth detection signal, wherein the first and second voltages have a constant voltage level, respectively.

2. The negative voltage supply device of claim 1 , wherein the third voltage is lowered as the temperature is raised.

3. The negative voltage supply device of claim 1 , wherein the third negative voltage detector detects a level of the negative voltage by using a first element and a second element, which have a different degree of change in their respective resistance values depending on temperature variations.

4. The negative voltage supply device of claim 3 , wherein the third negative voltage detector allows the first element to operate as a pull-up resistor and the second element to operate as a pull-down resistor, and generates the third detection signal by voltage distribution of the first element and the second element.

5. The negative voltage supply device of claim 4 , wherein the first element includes a PMOS transistor whose gate takes a ground voltage and source receives a higher voltage, the second element includes an NMOS transistor whose source receives the negative voltage and gate accepts the higher voltage, and the drains of the PMOS transistor and the NMOS transistor are connected to each other.

6. The negative voltage supply device of claim 5 , wherein the third negative voltage detector outputs the third detection signal through at least one inverter taking a voltage of the drain terminal.

7. The negative voltage supply device of claim 1 , wherein the clamping part causes the fourth detection signal having the same logic level as the third detection signal to be disabled when the first detection signal is disabled, and causes the fourth detection signal to be enabled when the second detection signal is enabled.

8. The negative voltage supply device of claim 7 , wherein the clamping part includes: a first NOR gate for logically combining the second detection signal and the third detection signal; and a second NOR gate for logically combining an inverted signal of the first detection signal and an output from the first NOR gate to output the fourth detection signal.

9. The negative voltage supply device of claim 8 , wherein the negative voltage pumping unit includes: an oscillator for generating a periodic signal in response to the fourth detection signal; a pump controller for outputting pump control signals in response to an output signal from the oscillator; and a charge pump for pumping the negative voltage in response to the pump control signals.